Bring a large pot of salted water to a boil. Cook fettuccine until al dente according to package directions. Reserve 1/2 cup pasta water, then drain the pasta.

Season the diced chicken with salt and pepper.

Heat olive oil in a large skillet over medium-high heat. Add chicken in a single layer and sear for 3–4 minutes without moving, then toss and cook another 2–3 minutes until cooked through and golden. Remove chicken to a plate.

Reduce heat to medium. Add minced garlic to the skillet and sauté for 30–45 seconds until fragrant — do not let it brown.

Pour in heavy cream and bring to a gentle simmer. Let it reduce for 2–3 minutes, stirring occasionally.

Lower heat and whisk in grated Parmesan until smooth. If the sauce seems too thick, add a splash of reserved pasta water to reach your desired consistency.

Return the cooked chicken to the skillet and stir to coat. Add the drained fettuccine and toss until everything is evenly coated. Taste and adjust salt and pepper.

Finish with chopped fresh parsley and serve immediately.